Lipopolysaccharides in Rhizobium-Legume Symbioses

Abstract

The establishment of nitrogen-fixing symbiosis between a legume plant and its rhizobial symbiont requires that the bacterium adapt to changing conditions that occur with the host plant that both promotes and allows infection of the host root nodule cell, regulates and resists the host defense response, permits the exchange of metabolites, and contributes to the overall health of the host. This adaptive process involves changes to the bacterial cell surface and, therefore, structural modifications to the lipopolysaccharide (LPS). In this chapter, we describe the structures of the LPSs from symbiont members of the Rhizobiales, the genetics and mechanism of their biosynthesis, the modifications that occur during symbiosis, and their possible functions.

Coupled Mass Spectrometric Strategies for the Determination of Carbohydrates at Very Low Concentrations: The Case of Polysaccharides Involved in the Molecular Dialogue Between Plants and Rhizobia

“…The LMW LPS, named rough LPS are composed of lipid A and core polysaccharides, whereas the HMW LPS (smooth LPS) are made of the 3 associated parts [101].…”

Roles of Predicted Glycosyltransferases in the Biosynthesis of the Rhizobium etli CE3 O Antigen

“…While the composition, structure, and synthesis of lipid A and core regions are often similar, especially between closely related species, the O-antigen portions can vary considerably even between strains of the same species (1,2). O antigens can consist of a polymer of a single sugar (homopolymer) or many different sugars (heteropolymer).…”

“…O antigens can consist of a polymer of a single sugar (homopolymer) or many different sugars (heteropolymer). In both types of polymers, the number of repeating units can be either fixed or varied, giving rise to O antigens of uniform and modal lengths, respectively (1,2).…”

“…Having homologs of wzm and wzt in the chromosomal O-antigen genetic cluster (Fig. 2), R. etli CE3 is postulated to synthesize its O antigen by the ABC transporter pathway (2,14,15). For this type of synthesis, the terms primer, adaptor, repeat-unit domain, and chain terminator have been proposed for different portions of the O-chain (1,4), as indicated in Fig.…”

“…Nearly all the genes required to synthesize the known R. etli CE3 O-antigen structure are located in three separate loci in the genome (2,14,16). Except for well-known orthologous genes, such as fcl and gmd, genes devoted to R. etli CE3 O-antigen synthesis have been given the designation wre ( Fig.…”